1. Field of the Invention
This invention relates to a boss for filament wound pressure vessels and particularly to an improved boss for filament wound pressure vessels that can withstand high pressure without leaking.
2. Description of the Prior Art
Pressure vessel of various types have been widely used in many applications. Propane gas tanks used as fuel storage in households, oxygen gas tanks used in laboratories and high pressure tanks used in the airplanes are but a few examples. A pressure vessel has to employ special structure, materials and design to withstand high fluid pressure without leaking. To meet this requirement, a conventional pressure vessel usually has a plastic liner, a filament wound outershell wrapping around the plastic liner, and a metallic boss. The metallic boss generally has a tubular neck and an annular flange engaging with the interior surface of the plastic to form a sturdy structure to withstand high internal pressure. The metallic boss requires substantial amounts of machining work. It is time consuming to make and is expensive.
U.S. Pat. No. 5,429,845 (Newhouse et al.) discloses a metallic boss which has an annular attachment flange with a skewed annular locking groove formed in the inner surface or outer surface of the attachment flange. While it may enhance the strength to support high pressure, it needs a great deal of machining work. It therefore costs higher.
U.S. Pat. No. 5,568,878 (Le Brefon) discloses another reinforced access opening for filament wound pressure vessel. It has a metallic cylindrical reinforcement member and a supporting flange at one end engaging with an annular face of the liner flange, and a radially extending supporting foot at its other end which contacts a mating outer surface of the liner. It has a sharp angle at one end of the supporting foot while another end of the supporting end is tapering off. The sharp angle could cause liner rupture under high pressure while the tapering end cannot form a strong binding with the liner and the outershell. Its resistance to high pressure is thus questionable.